<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style type="text/css">
  body{
    margin: 20px;
  }
  .container{
    border: 1px solid #ccc;
    padding: 10px;
    width: 300px;
    height: 300px;
  }
  .container .box{
    width: 100px;
    height:100px;
    border: 1px solid red;
  }
  </style>
</head>
<body>
  <p>一段文字 1</p>
  <p>一段文字 2</p>
  <p>一段文字 3</p>
  <div class="container">
    <div class="box">

    </div>
  </div>
  <script src="./async.js"></script>
</body>
</html>